The present invention relates to a portable thermal imager, a device that is commonly used by firefighters and other rescue personnel to identify the seat of a fire from outside of a burning structure, to identify fire conditions within a burning structure hidden by heavy smoke, and/or to identify victims trapped within a burning structure. Specifically, the present invention relates to a portable thermal imager with a shock-absorbing lens mount that minimizes the transfer of impact forces to the fragile lens, such as when the thermal imager is dropped.
Thermal imagers, also referred to as thermal imaging cameras, were introduced to firefighters in the mid-1990""s. Originally developed for military applications, thermal imagers quickly proved to be a valuable fire-fighting tool, essentially allowing firefighters to xe2x80x9cseexe2x80x9d in dark, smoke-filled and other extreme environments.
Thermal imagers can be used by firefighters in numerous applications, including: to identify the seat of the fire from outside of a burning structure, thereby allowing the incident commander to determine what resources will be necessary and how to deploy such resources; to identify fire conditions and xe2x80x9chot spotsxe2x80x9d within a burning structure hidden by heavy smoke or building design features; and to identify victims trapped within a burning structure despite potentially blinding smoke conditions. Furthermore, thermal imagers have been used to identify alternate egress routes for rapid and safe extraction of victims; to observe the impact of the water application on the heat and fire conditions; to identify areas within a burning structure with extremely high heat levels so such areas can be ventilated to reduce the chances of backdraft or flashover; to identify windows and doors in potentially blinding smoke conditions, thus allowing firefighters to rapidly vent a burning structure as they move through it; and to identify the movement of hazardous materials and identify product levels in containers within the burning structure.
Structurally, a portable thermal imager includes four primary components that are contained in a housing designed to be carried by an individual, e.g., a firefighter. First and foremost, the essential function of a thermal imager is carried out by a sensor (often referred to as a xe2x80x9ccameraxe2x80x9d) that reacts to infrared radiation, converting sensed thermal radiation (the xe2x80x9cthermal picturexe2x80x9d) of an area into a visible thermal image in which, relative to the surrounding environment, hotter areas appear white while cooler areas appear black. One of two sensors is commonly used in portable thermal imagers: (1) a barium strontium titanate (xe2x80x9cBSTxe2x80x9d) detector developed by the Raytheon Company of Lexington, Mass.; or (2) a microbolometer with a vanadium oxide (VOx) or an amorphous silicon sensing material, such as the LTC500 MicroIR(trademark) Imaging Camera manufactured and distributed by BAE Systems of Nashua, N.H.
The second primary component is a lens which focuses the thermal picture onto the sensor, specifically onto a focal plane array (xe2x80x9cFPAxe2x80x9d) of independent pixels. The quality of the lens is a major factor in the quality of the resultant thermal image. One measure of quality is the f-number. A wider lens means a smaller f-number and increased image quality. Of course, the width of the lens is limited by weight and costs considerations. For this reason, a common lens provides a field of view up to approximately 60xc2x0, and a common material for lens construction is germanium.
The third primary component is the video display, the means by which the resultant thermal image is provided to the user. An active matrix liquid crystal display (xe2x80x9cLCDxe2x80x9d) is commonly used in portable thermal imagers.
Finally, the fourth primary component is a power supply. A NiMH or similar rechargeable battery is commonly used in portable thermal imagers, although alkaline or other common batteries may be also used.
Again, each of the four above-described components is contained within (or otherwise secured to) a common housing. The housing protects the delicate sensing components, and indeed protects such components in even severe fire conditions. At the same time, common housings are designed to facilitate transport. In this regard, some portable thermal imagers are designed with a pistol grip that allows a firefighter to easily carry and aim the thermal imager; others are provided with straps that allow the thermal imager to be raised to the eyes much like binoculars. The underlying sensing and display technology of the thermal imager is well-developed and employed by various manufacturers.
As mentioned above, the lens is one of the primary components of a typical thermal imager and serves to focus the thermal picture onto the FPA of the sensor or camera However, the lens, which is often composed of germanium, is fragile and susceptible to breakage.
In prior art constructions, a lens typically is sealed on one or both of its broad faces with an O-ring or gasket. The lens and associated O-rings or gaskets are then compressed between a stationary outer wall of the thermal imager housing and another wall member or cap. However, should the impact to the wall member or cap be greater than can be absorbed by compressions of the O-rings or gaskets, the force may be translated to the lens, causing it to fracture or break. If the lens of the thermal imager is fractured or broken while in use, the imager can no longer properly function. Although the issue of the fragility of the lens is a recognized problem in the thermal imager industry, there has been no adequate solution that protects the lens during exposure in extreme environments.
It is therefore a paramount object of the present invention to provide a portable thermal imager with a shock-absorbing lens mount that protects the fragile lens from the forces of impact, such as when the thermal imager is dropped.
It is a further object of the present invention to provide a portable thermal imager with a shock-absorbing lens mount that is watertight even in severe heat and water conditions.
These and other objects and advantages of the present invention will become apparent upon a reading of the following description.
The present invention is a portable thermal imager with a shock-absorbing lens mount that minimizes the transfer of the impact forces to the fragile lens. Specifically, the lens of the portable thermal imager is encased within a circumferential grommet and then received in a cavity defined by the housing. In this regard, the housing defines a substantially circular opening therethrough which has a diameter that is less than that of the lens. A rim extends from the housing and circumscribes this opening, creating an annular ledge between the opening and the rim. The cavity is the cylindrical volume bounded by the rim.
When the lens and associated grommet are received in the cavity defined by the housing, the grommet is compressed along its circumferential edge against the internal wall of the rim, such that the lens is essentially suspended within the cavity. The lens itself does not contact the internal wall or the rim or any other portion of the housing.
The annular ledge serves to prevent the lens from being forced inside of the housing in the event of an especially large impact to the thermal imager. Similarly, to prevent the lens from being dislodged from the cavity in the opposite direction, a cap or bezel is secured to the rim of the housing over the lens.
Because of the construction described above, should the front end of the thermal imager be impacted, the bezel absorbs the forces of impact, translating such forces to the housing of the thermal imager. Since the lens is essentially suspended between the housing and the bezel, little or no force resulting from an impact to the thermal imager is translated to the lens.